Spare Parts

Maintenance Manual


Operation and Maintenance Instructions :

Polyhydron make Pilot Oil Units are reliable hence require very little attention from user. However it is necessary that following points must be kept in mind while storage, operation, commissioning and maintenance.

Storage :

The valve needs to be well lubricated to prevent the spool from getting stuck up in valve body due to possible corrosion. It should be properly covered to protect from dust/dirt.

Operation :

Hydraulic Pilot Oil Units operate on the basis of Direct Acting Pressure Reducing valves.

It is basically a variable orifice, the opening or closing of which is controlled by a (metering) spool.

In neutral position the element is held in the position by return spring. When the lever is operated against the spring, The flunger moves against the spring. At the same time, the controlling spool is pushed through the controlling spring. When the controlling stroke begins, then there is a connection from ‘P’ to port 1,2,3 & 4. Pressure adjustments are related to the position of the lever.

Switch type feature is used for additional electrical application.

Commissioning :

The things that should be attended to during commissioning are as follows:

The inlet line should be connected to the port P of the valve and the outlet to the ports 1,2,3 & 4 are for pilot controls

Tank port must be drained.

Maintenance :

To enhance the proper working of the valve it is necessary to attain the following points. :

The oil must be of prime quality and clean as per ISO code 16/13.

Contaminated oil may lead to the wear of the spool & swiveling unit there by increasing clearance between the pilot piston and housing. This results in the improper working of the valve.

The oil temperature must be within the specified range i.e. -20 C to +70 C.


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Subject to revision.

Regd. office & Works :
78-80, Machhe Industrial Estate, Machhe, Belgaum - 590 014. Karnataka, INDIA. 
Phone :
+91-0831-2411001.  Fax : +91-0831-2411002 ,  
E-mail : ,  Website :


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Updated on February 04, 2015 03:05 pm .